Our strategy in this program is to apply the knowledge acquired in recent years about the mechanisms of lymphocyte recognition, antigen processing and presentation, lymphocyte activation and programmed cell death, combined with new tools such as T cell receptor transgenic mice, and new in vitro models of lymphocyte response to directly investigate the basic biology of immune memory. We will characterize T and B memory cells and further develop in vitro and in vivo models in which their generation can be assessed. We will evaluate the factors which are required for memory cell generation, persistence and memory cell effectiveness. We will study the in vivo response of memory cells including their recirculation and homing. Having established fact[unreadable][unreadable]s which appear to be key in these steps, we will also examine their relevance in an influenza disease protection model. Project 1: Development of CD4 Memory (Swain), will focus on the generation of CD4 memory from in vitro generated effector cells. The roles of antigen stimulation and key cytokines and co-stimulatory interactions in driving effector expansion vs. death and in promoting transition of cells to a memory state will be determined in vitro and their physiologic importance evaluated in vivo. Project 2: Generation of CD8 Subsets and Memory (Dutton), will generate distinct subsets of CD8 effectors with polarized cytokine production and function. The ability of such effectors to give rise to memory and the effectiveness of the memory generated from different subsets will be determined. The roles of antigen ad cytokines in memory generation will be determined. The ability of CD8 subsets to protect against influenza and the regional distribution of CD8 memory cells will be evaluated. Project 3: Recirculation of Memory T Cells. (Bradley), will concentrate on in vivo studies addressing the molecular interactions that regulate where memory lymphocytes go and how they get there. These studies will include evaluations of efficient protocols for generating memory in immunological sites where it is needed. These investigations will include studies of mucosal sites, which are particularly relevant for protection to many infectious organisms. Project 4: Development of Memory B Cells (Klinman), will utilize on in vitro models in which memory B cells can be generated. The roles of antigen, T cell help, cytokines and co-stimulatory interactions on the production of memory B cells and the affinity of antibody they produce will be investigated. Together these studies will provide a comprehensive picture of some of the most important aspects regulating the development of memory including the roles of specific antigen and the interactions of the specific lymphocytes with one another, with other regulatory cells such as antigen-presenting cells and with their milieu. By combining their expertise and exchanging their findings the investigators will be able to capitalize on each others's observations and importantly design joint experiments which would not otherwise be feasible. We believe these studies will pinpoint aspects of memory generation that will provide the basis for rational vaccine development and for intervention in the immunization process with the potential to considerably enhance the efficacy of immunization.